Slugging the bore question?

Aren't the lands more important? don't the grooves just show how much depth the bullet can expand?
For instance I have heard of people with Tokarev's who slug the barrel and measure the grooves and get a .311 or .312 and freak out saying" the Tokarev is supposed to have a .308 barrel and mine is oversized!"
Ideally if a bore is supposed to be .308 shouldn't the grooves be .002 or .003 more?
If a bore(lands) is .308 should I buy bullets for .308 or .309 or what?

Unless the bullet is a Mini ball design with a thin rear shirt and a hollow center it will not expand much at all.

Click to expand...

You'd be amazed at how much a bullet will expand (obturate) when fired in an oversize barrel. When there's 50,000-60,000 psi behind it, all at once, the plastic limits of the bullet material (lead and copper) have been exceeded multifold. About the only bullets that don't are the "Solids" like Barnes.

Naturally, this is dependent on the gap not being all that excessive but a few thousandth's will definitely disappear when the charge goes off.

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